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Diffstat (limited to 'mmalloc/mmcheck.c')
| -rw-r--r-- | mmalloc/mmcheck.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/mmalloc/mmcheck.c b/mmalloc/mmcheck.c new file mode 100644 index 0000000..2a4b09e --- /dev/null +++ b/mmalloc/mmcheck.c @@ -0,0 +1,196 @@ +/* Standard debugging hooks for `mmalloc'. + Copyright 1990, 1991, 1992 Free Software Foundation + + Written May 1989 by Mike Haertel. + Heavily modified Mar 1992 by Fred Fish (fnf@cygnus.com) + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. + + The author may be reached (Email) at the address mike@ai.mit.edu, + or (US mail) as Mike Haertel c/o Free Software Foundation. */ + +#include "mmalloc.h" + +/* Default function to call when something awful happens. The application + can specify an alternate function to be called instead (and probably will + want to). */ + +extern void abort PARAMS ((void)); + +/* Arbitrary magical numbers. */ + +#define MAGICWORD 0xfedabeeb /* Magic word for active chunk */ +#define MAGICWORDFREE 0xdeadbeef /* Magic word for inactive chunk */ +#define MAGICBYTE ((char) 0xd7) + +/* Each memory allocation is bounded by a header structure and a trailer + byte. I.E. + + <size><magicword><user's allocation><magicbyte> + + The pointer returned to the user points to the first byte in the + user's allocation area. The magic word can be tested to detect + buffer underruns and the magic byte can be tested to detect overruns. */ + +struct hdr + { + size_t size; /* Exact size requested by user. */ + unsigned long int magic; /* Magic number to check header integrity. */ + }; + +/* Check the magicword and magicbyte, and if either is corrupted then + call the emergency abort function specified for the heap in use. */ + +static void +checkhdr (mdp, hdr) + struct mdesc *mdp; + CONST struct hdr *hdr; +{ + if (hdr -> magic != MAGICWORD || + ((char *) &hdr[1])[hdr -> size] != MAGICBYTE) + { + (*mdp -> abortfunc)(); + } +} + +static void +mfree_check (md, ptr) + PTR md; + PTR ptr; +{ + struct hdr *hdr = ((struct hdr *) ptr) - 1; + struct mdesc *mdp; + + mdp = MD_TO_MDP (md); + checkhdr (mdp, hdr); + hdr -> magic = MAGICWORDFREE; + mdp -> mfree_hook = NULL; + mfree (md, hdr); + mdp -> mfree_hook = mfree_check; +} + +static PTR +mmalloc_check (md, size) + PTR md; + size_t size; +{ + struct hdr *hdr; + struct mdesc *mdp; + size_t nbytes; + + mdp = MD_TO_MDP (md); + mdp -> mmalloc_hook = NULL; + nbytes = sizeof (struct hdr) + size + 1; + hdr = (struct hdr *) mmalloc (md, nbytes); + mdp -> mmalloc_hook = mmalloc_check; + if (hdr != NULL) + { + hdr -> size = size; + hdr -> magic = MAGICWORD; + hdr++; + *((char *) hdr + size) = MAGICBYTE; + } + return ((PTR) hdr); +} + +static PTR +mrealloc_check (md, ptr, size) + PTR md; + PTR ptr; + size_t size; +{ + struct hdr *hdr = ((struct hdr *) ptr) - 1; + struct mdesc *mdp; + size_t nbytes; + + mdp = MD_TO_MDP (md); + checkhdr (mdp, hdr); + mdp -> mfree_hook = NULL; + mdp -> mmalloc_hook = NULL; + mdp -> mrealloc_hook = NULL; + nbytes = sizeof (struct hdr) + size + 1; + hdr = (struct hdr *) mrealloc (md, (PTR) hdr, nbytes); + mdp -> mfree_hook = mfree_check; + mdp -> mmalloc_hook = mmalloc_check; + mdp -> mrealloc_hook = mrealloc_check; + if (hdr != NULL) + { + hdr -> size = size; + hdr++; + *((char *) hdr + size) = MAGICBYTE; + } + return ((PTR) hdr); +} + +/* Turn on default checking for mmalloc/mrealloc/mfree, for the heap specified + by MD. If FUNC is non-NULL, it is a pointer to the function to call + to abort whenever memory corruption is detected. By default, this is the + standard library function abort(). + + Note that we disallow installation of initial checking hooks if mmalloc + has been called at any time for this particular heap, since if any region + that is allocated prior to installation of the hooks is subsequently + reallocated or freed after installation of the hooks, it is guaranteed + to trigger a memory corruption error. We do this by checking the state + of the MMALLOC_INITIALIZED flag. + + However, we can call this function at any time after the initial call, + to update the function pointers to the checking routines and to the + user defined corruption handler routine, as long as these function pointers + have been previously extablished by the initial call. Note that we + do this automatically when remapping an previously used heap, to ensure + that the hooks get updated to the correct values, although the corruption + handler pointer gets set back to the default. The application can then + call mmcheck to use a different corruption handler if desired. + + Returns non-zero if checking is successfully enabled, zero otherwise. */ + +int +mmcheck (md, func) + PTR md; + void (*func) PARAMS ((void)); +{ + struct mdesc *mdp; + int rtnval; + + mdp = MD_TO_MDP (md); + + /* We can safely set or update the abort function at any time, regardless + of whether or not we successfully do anything else. */ + + mdp -> abortfunc = (func != NULL ? func : abort); + + /* If we haven't yet called mmalloc the first time for this heap, or if we + have hooks that were previously installed, then allow the hooks to be + initialized or updated. */ + + if (1 /* FIXME: Always allow installation for now. */ || + !(mdp -> flags & MMALLOC_INITIALIZED) || + (mdp -> mfree_hook != NULL)) + { + mdp -> mfree_hook = mfree_check; + mdp -> mmalloc_hook = mmalloc_check; + mdp -> mrealloc_hook = mrealloc_check; + mdp -> flags |= MMALLOC_MMCHECK_USED; + rtnval = 1; + } + else + { + rtnval = 0; + } + + return (rtnval); +} |